| During the construction and operation of tunnels,due to the influence of construction quality and complex geological environment conditions,the deterioration and disease problems of tunnel lining structures are gradually becoming prominent.Especially during tunnel operation,cases of disaster accidents such as water leakage,steel corrosion,lining deformation and cracking,and lining peeling off are common,posing a significant threat to the safety of tunnel operation.Among them,geological hazards behind the lining are the main factors that cause and exacerbate lining damage and disease problems.Therefore,conducting refined detection work on geological hazards behind the tunnel lining,revealing information such as the type,location,and scale of unfavorable geological bodies behind the lining,is of great significance for ensuring the stability and durability of the tunnel structure,saving operation and maintenance costs,and ensuring personnel and traffic safety.At present,for the detection of reinforced concrete lining in tunnels,commonly used electromagnetic methods such as ground penetrating radar(GPR)are severely affected by electromagnetic wave interference,with low detection accuracy,limited detection depth of ultrasonic methods.Tunnel engineering detection site space is limited.These problems to some extent restrict the development of geological hazard detection technology behind tunnel lining.Therefore,this article applies the seismic wave method that is not affected by electromagnetic interference to the detection of lining.Based on traditional seismic wave detection,a targeted seismic detection method with multiple coverages of small geological hazards behind tunnel lining is proposed.Its main characteristics are intermediate excitation,eight small arrays for reception,the same track spacing and offset,and rolling measurement.Overall,this method combines the advantages of seismic imaging and traditional multiple coverage methods,effectively improving the accuracy and efficiency of geological hazard detection behind tunnel lining.In addition,due to the use of non-explosive sources,the cost is low,easy to implement,and conducive to promotion.The main research is as follows:(1)The research on small array multiple coverage seismic method based on theoretical analysis is carried out,and the theoretical analysis of seismic wave method is carried out from kinematics characteristics such as seismic wave type and characteristics,propagation law,time distance curve,and dynamic characteristics such as waveform,resolution,amplitude and phase.Based on the characteristics of tunnel engineering,a small arrangement multiple coverage method has been proposed,which improves and improves the traditional multiple coverage on-site wiring and data collection methods,laying a theoretical foundation for subsequent application research.(2)According to the occurrence state of undesirable geological bodies in actual tunnel engineering,a variety of undesirable geological models were established for numerical simulation analysis,including karst cave,cavity,fault,fracture zone and complex comprehensive geological model,and the waveform response and imaging characteristics of different abnormal bodies detected by small array multiple coverage method were revealed.Secondly,the seismic mapping method is simulated for the same poor geological body model.Through comparative analysis,it is found that the small array multiple coverage method proposed in this paper is cleaner and clearer in detecting seismic profile imaging,and can suppress the interference of diffraction waves better.The small array multiple coverage method is more accurate in characterizing the boundaries of abnormal bodies,making the positioning of unfavorable geological bodies more accurate and improving the resolution of seismic wave detection methods.(3)The model test of detecting geological hidden danger behind lining by small array multiple coverage method was carried out,and the geological model of geological hidden danger behind lining including single anomaly body and multiple anomaly body of karst cave and cavity was established,and the validity of small array multiple coverage method applied in practical engineering was verified.By comparing the outdoor model test results with the numerical simulation results,the effectiveness of this method for fine detection of geological hidden dangers behind the tunnel lining is verified and can depict the distribution of geological abnormal bodies behind the lining more accurately.It has a good feature resolution and recognition ability for horizontal and vertical side-by-side multiple abnormal bodies.(4)Field application research of small array multiple coverage method was carried out.Combined with the Kaiyuan Tunnel operation and maintenance detection project in Jinan City,the grouting effect and lining disease behind the tunnel lining were detected,the grouting effect behind the tunnel lining was verified,the hidden geological hazards behind the tunnel lining were investigated,and the thickness of the tunnel lining was accurately detected,which was compared with the geological radar method.The advantages of the small array multiple coverage method in anti-interference ability,detection depth,and imaging accuracy are verified. |
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